question_answer 1)

Construct \[{{l}_{5}}\] of length 7.8 cm. From this, cut off \[{{l}_{1}},{{l}_{2}}\] of length 4.7 cm. Measure \[{{l}_{3}}\]

Answer:

                Given, \[{{l}_{1}},{{l}_{2}},{{l}_{3}}\]and \[{{l}_{4}}\]Now, to construct a line segment of length 7.8 cm, we use the following steps: Step I Draw a line \[l\]. Mark a point A on this line. Step II Place the pointer of compasses at the zero mark of the ruler. Open it to place the pencil point up to the 7.8 cm mark. Step III Without changing the opening to the compasses. Place the pointer on A and swing an arc to cut \[l\] at B. Step IV \[{{l}_{1}}\] is a line segment of length 7.8 cm.          Now, to cut off \[{{l}_{2}}\] of length 4.7 cm from \[{{l}_{1}}\] we use the following steps: Step V Now, place the pointer of compasses at the zero mark of the ruler. Open it to the place the pencil point upto 4.7 cm mark. Step VI Without changing the opening of the compasses, place the pointer on A and swing an arc to cut \[l\] at C. Step VII Now, \[{{l}_{1}}\] is a line segment of length 4.7 cm. On measuring, we get \[{{l}_{2}}\]